Solid rocket motors may be utilized in weapons such as air-to-air and air-to-ground missiles, as well as in model rockets and boosters for satellite launchers. Air pockets within the propellant grain or fractures of the grain may produce an instantaneous increase in burn surface area. The increase in burn surface area may produce a corresponding increase in exhaust gas and pressure, which may result in a rupture of the casing containing the propellant.
Aging of the propellant may lead to significant degradation in weapon performance and catastrophic failure. Tactical missiles may be kept for extended periods of time and, accordingly, there is a dire need to know if there is any defect in the propellant prior to use.
An aging model may be used to predict and detect material degradation, given an assumed or measured environmental history. Other approaches may use non-destructive testing, such as ultrasound and X-rays. All of these approaches, as currently practiced, may be inadequate to meet the needs of a real-time self-sensing monitoring system for full-up rounds. In addition, the rounds may not be able to be examined in-situ, but must be removed from their storage location and brought to an examining machine.
In addition to the above approaches, other testing methods may include the use of embedded sensors, such as fiber optics or electrical strain gages. Drawbacks to these methods include fragility, difficulty in placement during manufacture, and the need for expensive and bulky interrogators.